System for producing transportation fuels from waste plastic and biomass

ABSTRACT

The present invention is generally directed to methods and systems for producing biofuels via biomass, waste plastic, and/or Fischer-Tropsch product feeds. Such methods and systems are an improvement over the existing art at least in that they are feed-tolerant (i.e., allow for variability) and provide an economy of scale, while typically retaining the environmental benefits associated with such processing of such feeds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Divisional of U.S. patent application Ser. No.11/955,130, filed Dec. 12, 2007.

FIELD OF THE INVENTION

This invention relates generally to methods and systems for processingwaste plastic and biomass into usable products, and specifically tomethods and systems for pyrolyzing waste plastic and biomass feeds in acommon pyrolysis unit en route to the production of transportationfuels.

BACKGROUND

1. Waste Plastic

There is a steadily increasing demand for technology capable ofconverting discarded and waste plastic materials into useful products.This is due in large measure to public concerns over potentialenvironmental damage caused by the presence of these waste materials.According to a recent report from the Office of Solid Waste, about 62%of plastic packaging in the United States is made of polyethylene, thepreferred feed for processing waste plastics. Plastics waste is thefastest growing waste product, with about 18 million tons per year in1995 compared to only four million tons per year in 1970, and thisamount is growing by approximately 10% per year. Transforming plasticwaste material and particularly polyethylene into useful productspresents a unique opportunity to address a growing environmentalproblem.

Methods for converting such above-mentioned waste plastic intolubricating oils have been described previously. See, e.g., U.S. Pat.Nos. 6,150,577 (Miller et al.) and 6,822,126 (Miller), both of whichpertain to the production of high viscosity index (VI) lubricating oilsfrom a primarily polyolefin waste plastic feedstock.

2. Biofuels

Many methods have been suggested for utilizing biofuels for energyproduction in order to compensate for at least a portion of the fossilfuel currently used in such energy production, and thereby also decreasenet CO₂ emissions in the overall energy production cycle. Unfortunately,biofeedstocks are generally considered to be low energy fuels, and noteasily utilized for energy production. The low energy content of biomassrenders it generally inadequate for high-efficiency production ofenergy, such as high-temperature, high-pressure steam or electricity.Additionally, non-uniformity in the raw material (i.e., biomass),differences in its quality, and other similar hard-to-controlvariations, may cause problems in an energy production cycle that reliesheavily on such fuel.

In view of the foregoing, methods and/or systems for integrating biofuelprocessing with waste plastic processing would be extremelyuseful—particularly wherein such processing provides for biofuelproducts, and wherein such processing can serve to ameliorate ormitigate at least some of the limitations typically associated with theprocessing of biomass.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is generally directed to methods and systems forproducing biofuels via a combination of biomass, waste plastic, and/orFischer-Tropsch product feeds. Such methods and systems are animprovement over the existing art at least in that they arefeed-tolerant (i.e., allow for variability) and provide an economy ofscale, while typically retaining the environmental benefits generallyassociated with the processing of such feeds.

In some embodiments, the present invention is directed to one or moremethods comprising the steps of: (a) pyrolyzing biomass concurrentlywith a second material such as waste plastic and/or Fischer-Tropsch wax,so as to yield pyrolysis oil; (b) separating the pyrolysis oil into atleast two component fractions according to boiling range; (c)hydrotreating at least one of the at least two component fractions so asto yield at least one hydrotreated intermediate; and (d)catalytically-isomerizing the at least one hydrotreated intermediate soas to yield at least one isomerized product.

In some or other embodiments, the present invention is directed to oneor more systems comprising: (a) a pyrolysis unit; (b) at least two feedsin communication with said pyrolysis unit, said at least two feedscomprising (i) a biomass feed, and (ii) at least one of a waste plasticfeed and a Fischer-Tropsch waxy feed, wherein the at least two feeds canbe channeled into the pyrolysis unit sequentially or simultaneously soas to produce pyrolysis oil, and wherein each feed can be varied so asto modulate the properties of the pyrolysis oil so produced; (c) aseparation unit for separating the pyrolysis oil into at least twopyrolyzed component fractions according to their boiling range; (d) ahydrotreating unit for hydrotreating at least one of the pyrolyzedcomponent fractions so as to yield one or more hydrotreated fractions;and (e) an isomerization unit for catalytically-isomerizing at least oneof the hydrotreated fractions so as to yield at least one isomerizedproduct.

The foregoing has outlined rather broadly the features of the presentinvention in order that the detailed description of the invention thatfollows may be better understood. Additional features and advantages ofthe invention will be described hereinafter which form the subject ofthe claims of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts, in flow diagram form, a method for concurrentlyprocessing biomass with at least one other feed, in accordance with someembodiments of the present invention; and

FIG. 2 is a schematic illustrating a system for producing fuel productsfrom a multiplicity of feeds, in accordance with some embodiments of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, the present invention is generally directed tomethods and systems for producing biofuels via pyrolysis of biomass,waste plastic, and/or Fischer-Tropsch (FT) product feeds/feedstocks.Such method embodiments generally involve the simultaneous pyrolysis ofbiomass with waste plastic and/or a FT wax. Such system embodimentstypically involve combining a biomass feed with a waste plastic and/orF-T waxy feed, and regulating the relative amount of each feed beingdirected into a pyrolysis unit for the production of a pyrolysis oil (pyoil) that is subjectable to further processing. Such further processingcan include hydroprocessing and/or isomerization and can yield,depending on conditions and feeds, a variety of biofuel products.

1. Definitions

Certain terms are defined throughout this description as they are firstused, while certain other terms used in this description are definedbelow:

“Biofuel,” as defined herein, is a fuel product at least partly derivedfrom “biomass,” the latter being a renewable resource of biologicalorigin.

A “feedstock,” as used herein, refers to hydrocarbonaccous material fedinto one or more of the systems or processes of the present invention inorder to make a fuel, lubricant, or other commercial product.

A “feed,” as defined herein, is a feedstock-carrying conduit, typicallybeing feedstock specific (i.e., dedicated to a specific feedstock).

A “gasifier,” as defined herein, refers to a reaction environmentwherein condensed hydrocarbonaceous feedstock material is converted intoa gas through the action of heat and, possibly, one or more reactivegases such as oxygen, air, carbon dioxide (CO₂), and/or steam.

“Synthesis gas,” or “syngas,” as defined herein, generally refers to amixture of carbon monoxide (CO) and hydrogen (H₂) produced bygasification in a gasifier.

As mentioned above, syngas can be catalytically-converted to paraffins(alkanes) via a catalytic Fischer-Tropsch (FT) process:nCO+(2n+1)H₂→C_(n)H_((2n+2)) +nH₂Owhere typical catalysts include iron and cobalt. Examples of theFisher-Tropsch process are described in U.S. Pat. No. 6,846,402.

“Pyrolyzing,” as defined herein, refers to a thermal processing and/orthermal decomposition of hydrocarbonaceous material, wherein saiddecomposition is typically carried out in a non-oxidative environment.

“Pyrolysis oil,” as defined herein, refers to a liquid hydrocarbonproduct resulting from the pyrolyzing treatment of hydrocarbonaceousmaterial.

“Hydroprocessing” or “hydrotreating” refers to processes or treatmentsthat react a hydrocarbon-based material with hydrogen, typically underpressure and with a catalyst (hydroprocessing can be non-catalytic).Such processes include, but are not limited to, hydrodeoxygenation (ofoxygenated species), hydrotreating, hydrocracking, hydroisomerization,and hydrodewaxing. For examples of such processes, see Cash et al., U.S.Pat. No. 6,630,066; and Elomari, U.S. Pat. No. 6,841,063. Embodiments ofthe present invention utilize such hydroprocessing to converttriglycerides to paraffins. The terms “hydroprocessing” and“hydrotreating” are used interchangeably herein.

“Isomerizing,” as defined herein, refers to catalytic processes thattypically convert n-alkanes to branched isomers. ISODEWAXING (Trademarkof CHEVRON U.S.A. INC.) catalysts are representative catalysts used insuch processes. See, e.g., Zones et al., U.S. Pat. No. 5,300,210;Miller, U.S. Pat. No. 5,158,665; and Miller, U.S. Pat. No. 4,859,312.

“Transportation fuels,” as defined herein, refer to hydrocarbon-basedfuels suitable for consumption by vehicles. Such fuels include, but arenot limited to, diesel, gasoline, jet fuel and the like.

“Diesel fuel,” as defined herein, is a material suitable for use indiesel engines and conforming to the current version at least one of thefollowing specifications: ASTM D 975—“Standard Specification for DieselFuel Oils”; European Grade CEN 90; Japanese Fuel Standards JIS K 2204;The United States National Conference on Weights and Measures (NCWM)1997 guidelines for premium diesel fuel; and The United States EngineManufacturers Association recommended guideline for premium diesel fuel(FQP-1A).

2. Methods

Referring to the flow diagram in FIG. 1, in some embodiments, thepresent invention is directed to one or more methods or processescomprising the steps of: (Step 101) pyrolyzing biomass concurrently witha second material selected from the group consisting of waste plastic,Fischer-Tropsch wax, and combinations thereof, so as to yield pyrolysisoil; (Step 102) separating the pyrolysis oil into at least two componentfractions according to boiling range; (Step 103) hydrotreating at leastone of the at least two component fractions so as to yield at least onehydrotreated intermediate; and (Step 104) catalytically-isomerizing theat least one hydrotreated intermediate so as to yield at least oneisomerized product.

In some such above-mentioned method embodiments, the pyrolyzing iscarried out by contacting a biomass feedstock and a second materialfeedstock in a pyrolysis zone at pyrolysis conditions, where at least aportion of the feed(s) is cracked, thus forming a pyrolysis zoneeffluent comprising l-olefins and n-paraffins. Pyrolysis conditionsinclude a temperature of from about 400° C. to about 700° C., preferablyfrom about 450° C. to about 650° C. Conventional pyrolysis technologyteaches operating conditions of above-atmospheric pressures. See, e.g.,U.S. Pat. No. 4,642,401. Additionally, it has been discovered that byadjusting the pressure downward, the yield of a desired product can becontrolled. See, e.g., U.S. Pat. No. 6,150,577. Accordingly, in someembodiments where such control is desired, the pyrolysis pressure issub-atmospheric.

In some such above-mentioned method embodiments, the biomass comprisesmaterial selected from the group consisting of cellulosic biomass,triglyceride-containing biological oils, lignin, hemicellulose, starch,and combinations thereof. Those of skill in the art will recognize that,depending on the desired products and processing conditions, and also oneconomic factors, some types of biomass will be more preferred thanothers. Those of skill in the art will further recognize that there willbe variability in the upper limits of the percent biomass in the overallfeed—depending on the nature of the feed and the product(s) desired.

In some such above-mentioned method embodiments, the second material iswaste plastic, wherein said waste plastic comprises at least about 75wt. % polyolefins, preferably at least about 80 wt. % polyolefins, andmore preferably at least about 90 wt. % polyolefins.

In such embodiments where a Fischer-Tropsch waxy feedstock is employed,the FT wax is typically characterized as a product comprising paraffinsand alpha (α) olefins having 30 or more carbon atoms each.

An advantage of at least some of the above-mentioned method embodimentsresides in that the relative amounts of biomass and second materialbeing concurrently pyrolyzed can be varied. Such variability can beeffected “on-the-fly,” so as to continue to produce uniform product fromvarying feed, thereby increasing processing efficiency.

In some such above-described method embodiments, the step of separatingemploys a distillation technique. Such distillation techniques arewell-known to those of skill in the art, particularly refining. Briefly,such techniques serve to separate a mixture into “fractions” or “cuts”based upon their boiling range. When temperatures required to separateparticular fractions become too high, cracking and other decompositionprocesses can ensue. In some such circumstances, vacuum flashing can beemployed to effect such separations. A common cut point for suchdistilling operations is 650° F., the temperature separating light gasoil or diesel from heavy gas oil. Accordingly, in some suchabove-mentioned method embodiments, the at least two component fractionscomprise a 650° F.− fraction (boiling below 650° F.) and a 650° F.+fraction (boiling above 650° F.).

In some such above-described method embodiments, the step ofhydrotreating involves a hydroprocessing/hydrotreating catalyst and ahydrogen-containing environment. In some such embodiments, the activehydrotreating catalyst component is a metal or alloy selected from thegroup consisting of cobalt-molybdenum (Co—Mo) catalyst,nickel-molybdenum (Ni—Mo) catalyst, noble metal catalyst, andcombinations thereof. Such species are typically supported on arefractory oxide support. Hydrotreating conditions generally includetemperature in the range 350° C.-450° C. and pressure in the range ofabout 4.8 MPa to about 15.2 MPa. For a general review ofhydroprocessing/hydrotreating, see, e.g., Rana et al., “A Review ofRecent Advances on Process Technologies for Upgrading of Heavy Oils andResidua,” Fuel, vol. 86, pp. 1216-1231, 2007. For an example of howtriglycerides can be hydroprocessed to yield a paraffinic product, seeCraig et al., U.S. Pat. No. 4,992,605.

In some such above-described embodiments, the step ofcatalytically-isomerizing results in superior fuel properties relativeto those of the non-isomerized product. In some such embodiments, thestep of isomerizing is carried out using an isomerization catalyst.Suitable such isomerization catalysts can include, but are not limitedto Pt or Pd on a support such as, but further not limited to, SAPO-11,SM-3, SSZ-32, ZSM-23, ZSM-22; and similar such supports. In some orother embodiments, the step of isomerizing comprises use of a Pt or Pdcatalyst supported on an acidic support material selected from the groupconsisting of beta or zeolite Y molecular sieves, SiO₂, Al₂O₃,SiO2-Al₂O₃, and combinations thereof. In some such embodiments, theisomerization is carried out at a temperature between about 500° F. andabout 750° F. The operating pressure is typically 200 to 2000pounds-force per square inch gauge (psig), and more typically 200 psigto 1000 psig. Hydrogen flow rate is typically 50 to 5000 standard cubicfeet/barrel (SCF/barrel). For other suitable isomerization catalysts,see, e.g., Zones et al., U.S. Pat. No. 5,300,210; Miller, U.S. Pat. No.5,158,665; and Miller, U.S. Pat. No. 4,859,312.

With regard to the catalytically-driven isomerizing step describedabove, in some embodiments, the methods described herein may beconducted by contacting the n-paraffinic product with a fixed stationarybed of catalyst, with a fixed fluidized bed, or with a transport bed. Inone presently contemplated embodiment, a trickle-bed operation isemployed, wherein such feed is allowed to trickle through a stationaryfixed bed, typically in the presence of hydrogen. For an illustration ofthe operation of such catalysts, see Miller et al., U.S. Pat. Nos.6,204,426 and 6,723,889.

In some such above-mentioned method embodiments, the at least oneisomerized product yielded in the step of catalytically-isomerizing is atransportation biofuels, of which biodiesel is representative.

3. Systems

Referring to FIG. 2, in some embodiments, the present invention isdirected to one or more systems, such as system 200, said systemcomprising: a pyrolysis unit 201; at least two feeds in communicationwith said pyrolysis unit 201, said at least two feeds comprising (i) abiomass feed 25, and (ii) at least one of a waste plastic feed 20 and aFischer-Tropsch waxy feed 26, wherein the at least two feeds can bechanneled into the pyrolysis unit 201 via conduit 30 either sequentiallyor simultaneously so as to produce pyrolysis oil 40, and wherein eachfeed can be varied so as to modulate the properties of the pyrolysis oilso produced; a separation unit 203 for separating the pyrolysis oil intoat least two pyrolyzed component fractions 50 according to their boilingrange (e.g., Fractions A-C); a hydrotreating unit 207 for hydrotreatingat least one of the pyrolyzed component fractions, fed from separationzone 204 (note that the separation zone is separately defined as beingthe source(s) from which one or more fractions provided for additionalprocessing), so as to yield one or more hydrotreated fractions 60; andan isomerization unit 209 for catalytically-isomerizing at least one ofthe hydrotreated fractions so as to yield at least one isomerizedproduct 70.

In some such above-mentioned system embodiments, there further comprisesa regulating unit 202 for individually controlling the rate at whicheach teed is fed into the pyrolysis unit. Such a regulating unit enablesthe ability to produce a uniform product or products when the feedvaries (see above). Additionally or alternatively, regulating unit 202can serve to modulate the properties of the produced pyrolysis oil.

In some such above-mentioned system embodiments, there are at leastthree feeds in communication with the pyrolysis unit, said feedscomprising (i) a biomass feed, (ii) a waste plastic feed, and (iii) aFischer-Tropsch waxy feed. Depending on feedstock availability,processing conditions, and desired product(s), one or more of said feedsmay cease supplying feedstock to the pyrolysis unit.

Note that in some such above-mentioned system embodiments, theFischer-Tropsch waxy feed is supplied from an integrated gas-to-liquids(GTL) processing unit. There is, however, generally no proximalrequirement for the feedstock source in relation to system 200, suchconsiderations generally being of an economic or logistical nature.

Generally, all of the above-described system units are at least soconfigured so as to be operable for implementing one or more of themethods described in Section 2.

4. Conclusion

In summary, the present invention is directed generally to methods andsystems for producing biofuels via biomass, waste plastic, and/orFischer-Tropsch product feeds. Such methods and systems provide animprovement over the existing art at least in that they arefeed-tolerant (i.e., allow for variability) and provide an economy ofscale, while typically retaining the environmental benefits associatedwith the processing of such feeds.

All patents and publications referenced herein are hereby incorporatedby reference to the extent not inconsistent herewith. It will beunderstood that certain of the above-described structures, functions,and operations of the above-described embodiments are not necessary topractice the present invention and are included in the descriptionsimply for completeness of an exemplary embodiment or embodiments. Inaddition, it will be understood that specific structures, functions, andoperations set forth in the above-described referenced patents andpublications can be practiced in conjunction with the present invention,but they are not essential to its practice. It is therefore to beunderstood that the invention may be practiced otherwise than asspecifically described without actually departing from the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A system comprising: a) a pyrolysis unit; b) atleast two feeds in communication with said pyrolysis unit, said at leasttwo feeds comprising (i) a biomass feed, and (ii) at least one of awaste plastic feed and a Fischer-Tropsch waxy feed, wherein the at leasttwo feeds are configured to channel the at least two feeds into thepyrolysis unit sequentially or simultaneously so as to produce pyrolysisoil, and wherein the at least two feeds are separated from the pyrolysisunit by a regulatory unit configured to individually control the rate atwhich each feed is fed into the pyrolysis unit such that each feed isvaried so as to produce a uniform product or products from a non-uniformfeed; c) a separation unit for separating the pyrolysis oil into atleast two pyrolyzed component fractions according to their boilingrange; d) a hydrotreating unit for hydrotreating at least one of thepyrolyzed component fractions so as to yield one or more hydrotreatedfractions; and e) an isomerization unit for catalytically-isomerizing atleast one of the hydrotreated fractions so as to yield at least oneisomerized product.
 2. The system of claim 1, wherein the separationunit utilizes a distillation technique.
 3. The system of claim 1,wherein the hydrotreating unit comprises a supported active catalystcomponent, said component being selected from the group consisting ofCo—Mo, Ni—Mo, noble metals, and combinations thereof.
 4. The system ofclaim 1, wherein the isomerization unit comprises a supported noblemetal isomerization catalyst.
 5. The system of claim 1, wherein thereare at least three feeds in communication with the pyrolysis unit, saidfeeds comprising (i) a biomass feed, (ii) a waste plastic feed, and(iii) a Fischer-Tropsch waxy feed.
 6. The system of claim 5, furthercomprising an integrated gas-to-liquids processing unit in communicationwith the Fischer-Tropsch waxy feed.
 7. The system of claim 1, whereinthe regulatory unit is configured to control the rate at which each feedis fed into the pyrolysis unit on-the-fly.
 8. A system comprising: a) apyrolysis unit; b) at least three feeds in communication with saidpyrolysis unit, said at least three feeds comprising (i) a biomass feed,(ii) a waste plastic feed, and (iii) a Fischer-Tropsch waxy feed,wherein the at least three feeds are configured to channel the at leastthree feeds into the pyrolysis unit sequentially or simultaneously so asto produce pyrolysis oil, and wherein the at least three feeds areseparated from the pyrolysis unit by a regulatory unit configured toindividually control the rate at which each feed is fed into thepyrolysis unit; c) a separation unit for separating the pyrolysis oilinto at least two pyrolyzed component fractions according to theirboiling range; d) a hydrotreating unit for hydrotreating at least one ofthe pyrolyzed component fractions so as to yield one or morehydrotreated fractions; and e) an isomerization unit forcatalytically-isomerizing at least one of the hydrotreated fractions soas to yield at least one isomerized product.